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150 OPERATIVE DENTISTRY

that they are a trade enamel, that they are artificial when replaee-
ing the lost enamel of human teeth, that they are cement
when used to hold a filling of other material in the tooth or when
the material itself adheres to the tooth, and that they are not cement
(a noun) when used as a filling per se.
The author therefore takes the position that the filling material
under consideration is ''silicate" as the correct manipulation of most
makes eliminates adhesion to the cavity. Those which adhere to the
cavity or will retain fillings of other materials in the cavity are for
that reason a silicate cement. It therefore follows that with the use
of silicate there must be retentive form in cavity preparation. At

Fig. 81. Fig. 82.
Fig. 81.—Extensive Class Three cavity properly prepared for a silicate filling. Decay
shown in Fig. 79.
Fig. 82.—A Class Five and a Class Three cavity suitable for the use of silicate as a filling.
this time we find the best illustrations of this class of silicate in " De
Trey's Synthetic Porcelain" and Ascher's ''Artificial Enamel,"
neither of which should be used as a cement.
Cavity Preparation is quite similar to that for an amalgam filling
and is here considered in the order of cavity procedure.
Gaining Access. The access required for the silicate filling is the
same as that for any other plastic filling, as far as its introduction
is considered and the conditions sought at the time the filling is com-
pleted. Contact point in Classes Two, Three and Four is just as
essential, but is harder to maintain due to interproximal wear. It